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<H2><A NAME="s1">1.</A> <A HREF="blob.html#toc1">BLOB (Binary Large OBjects)</A></H2>

<P>This chapter is intended to give you a quick introduction to BLOBs, 
their interface as proposed for PHPLIB.</P>

<H2><A NAME="ss1.1">1.1</A> <A HREF="blob.html#toc1.1">Defining the problem</A>
</H2>

<P>Achieving the goal of creating portable applications is hindered by
the fact that no portable way of storing large amount of data
exists.</P>
<P>Every database vendor defines his own application programming
interface (API) to access binary large objects, or uses other, 
non-standard ways to enable the use of BLOBs.</P>
<P>Enhancing the existing vendor neutral support for databases in
PHPLIB to also include BLOB support could be a short-term solution
to the problem.</P>

<H2><A NAME="ss1.2">1.2</A> <A HREF="blob.html#toc1.2">Proposed extension API</A>
</H2>


<P>An overview over the function calls follows.</P>
<P>
<DL>
<DT><B>blob_create()</B><DD>
<P>This will create a new BLOB and return its ID. If it is impossible
to create a new BLOB, this function will <CODE>halt()</CODE> the execution
and generate an error message.</P>

<DT><B>blob_open($ID)</B><DD>
<P>Opens the specified BLOB for reading and writing and returns true or false
on success or failure, respectively.</P>

<DT><B>blob_close($ID)</B><DD>
<P>Closes the referenced BLOB. Do not forget this - it might be necessary
for some databases or you might face data loss.</P>

<DT><B>blob_delete($ID)</B><DD>
<P>Deletes the specified BLOB. All associated resources are freed.
The BLOB must not be referenced at a later time.</P>

<DT><B>blob_read($ID)</B><DD>
<P>Reads the entire data of BLOB and returns it.</P>

<DT><B>blob_write($ID, $DATA)</B><DD>
<P>Overwrites the whole BLOB with $DATA. </P>

</DL>
</P>

<H2><A NAME="ss1.3">1.3</A> <A HREF="blob.html#toc1.3">Design notes</A>
</H2>

<P>The goal was to create a vendor neutral API which could be implemented
easily with most databases. Eventually, it should provide a
"fallback" mode enabling the user to utilize BLOBs even if the
database does not support BLOBs natively. Keep in mind that it
should be able to cover as many databases as possible and therefore
only implements a subset of functionality provided by modern
databases.</P>

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